Various electronic apparatuses such as mobile phones have been widely used, and it has been demanded to further reduce size and weight of the electronic apparatuses and to achieve their longer lives. Accordingly, small and light-weight secondary batteries that have ability to achieve high energy density have been developed as power sources for the electronic apparatuses.
Note that applications of the secondary batteries are not limited to the electronic apparatuses described above, and it has been also considered to apply the secondary batteries to various other applications. Examples of such other applications may include: a battery pack attachably and detachably mounted on, for example, an electronic apparatus; an electric vehicle such as an electric automobile; an electric power storage system such as a home electric power server; and an electric power tool such as an electric drill.
The secondary battery includes a cathode, an anode, and electrolytic solution. The configuration of the secondary battery exerts a large influence on battery characteristics. Accordingly, various studies have been conducted on the configuration of the secondary battery.
More specifically, in order to obtain a high voltage, a bipolar secondary battery has been proposed (refer to International Publication No. WO 2010/010717). In the bipolar secondary battery, an intermediate electrode is provided between a cathode and an anode, and the intermediate electrode includes a cathode active material layer and an anode active material layer.